Patent GB-464631-A (GB)
Title: Improvements in and relating to mercury boilers
IPC: F22B3/02
Filed: 1936-12-10
Abstract: 464,631. Mercury-vapour generators. BRITISH THOMSON-HOUSTON CO., Ltd. Dec. 10, 1936, No. 33967. Convention date, Dec. 13, 1935. [Class 122 (iii)] [Also in Group XII] Comprises a combined natural and forced circulation type of mercury boiler with heating- elements lining the walls of a combustion chamber and connected to a mercury drum to which the vapour passes, and another chamber heated by gases from the first chamber and provided with additional heating-elements from which vapour passes to the drum. The mercury is forced through the first set of heating- elements by a pump but circulates in the second set of elements through heat and gravity. The lower section of the boiler rests on a foundation an upper section is supported by beams 12, 13; an intermediate section forms sliding joints 14, 15 with the lower and upper section respectively, and is supported resiliently by beams 17. The drum 19 has front and rear heads 20, 21 disposed partly outside the furnace walls 10. Between the lower and intermediate sections is a combustion chamber 22 lined by walls of heating-tubes 23. The upper ends of the side wall tubes are connected to the drum 19. The intermediate portions of the side tubes are twisted in groups to form slag screens. The arrangement reduces the supply of heat to the tubes by radiation and convection. The lower ends of the tubes 23 pass to external headers 26 connected by branched tubes 28, 29 to the drum 19. The headers 20, 21 and drum 19 have displacement blocks. Normal, thermal circulation of mercury by gravity takes place in the drum 19, tubes 27 ... 30, lower headers 26, and tubes 23. The discharge, combustion gases pass to an upper chamber to heat and evaporate mercury conducted to heating- elements fed from the drum 19 and an external source such as a condenser or condenser boiler. The elements comprise four banks of hair-pin bent tubes on each side of a vertical plane through the drum. The bank 32 forms a preheater fed through drums 34 from an external source. This bank is connected to headers 36 connected to a circulating-pump 40 driven by a variable speed motor 41<1> controlled by the load. The connecting conduit 39 is also fed from the drum 19. The mercury is pumped to banks of tubes 43, 44 on each side of the boiler, arranged above the roped tubes 23. The outlets of the. second and third banks of tubes are connected to the inlets of a fourth bank 50, the tubes of which are larger, carry vapour or fog, and are transversely arranged above the drum. The fourth bank tubes are each connected to pairs of second and third bank tubes. A baffle 53 protects the outlets. of tubes 50. These tubes are supported on the intermediate section and resiliently by rods 54 and plates 57. The tubes are shaped and lagged to protect the rods. The gases discharge through flue 60. The heating-elements of the boiler form two circuits with natural and forced circulation respectively. The circulation in the second, third and fourth tube banks is effected by the pump. The liquid in the tubes 43, 44 is subject to the pressure head in tubes 50. A drum pressure of 155 lbs. and a pump pressure of 510 lbs. gives a pressure at the entrance of tubes 50 of 350 lbs. per square inch. Fall of pressure and heat permits vaporization in these tubes. Clean surfaces may be ensured and ferrous surfaces protected as described in Specification 425,344. Specification 388,610 also is referred to.